15-hydroxy-prostaglandin dehydrogenase (15-PGDH) represents the key enzyme in the inactivation of a number of active prostaglandins, leukotrienes and hydroxyeicosatetraenoic acids (HETEs) (e.g., by catalyzing oxidation of PGE2 to 15-keto-prostaglandin E2, 15 k-PGE). The human enzyme is encoded by the HPGD gene and consists of a homodimer with subunits of a size of 29 kDa. The enzyme belongs to the evolutionarily conserved superfamily of short-chain dehydrogenase/reductase enzymes (SDRs), and according to the recently approved nomenclature for human enzymes, it is named SDR36C1. Thus far, two forms of 15-PGDH have been identified, NAD+-dependent type I 15-PGDH and the type II NADP-dependent 15-PGDH, also known as carbonyl reductase 1 (CBR1, SDR21C1). However, the preference of CBR1 for NADP and the high Km values of CBR1 for most prostaglandin suggest that the majority of the in vivo activity can be attributed to type I 15-PGDH.
Recent studies suggest that inhibitors of 15-PGDH and activators of 15-PGDH could be therapeutically valuable. It has been shown that there is an increase in the incidence of colon tumors in 15-PGDH knockout mouse models. A more recent study implicates increased 15-PGDH expression in the protection of thrombin-mediated cell death. It is well known that 15-PGDH is responsible for the inactivation of prostaglandin E2 (PGE2), which is a downstream product of COX-2 metabolism. PGE2 has been found to be neurotoxic both in vitro and in vivo; thus, COX-2 specific inhibitors, which decrease PGE2 release, exhibit neuroprotective effects. PGE2 has also been shown to be beneficial in a variety of biological processes, such as hair density, dermal wound healing, and bone formation.